We're ready to deploy our JsonRpcInterface. But right now now it just
returns JsonError::MethodNotFound. So before testing out the JSON-RPC,
let's implement some methods.
We'll start with a simple pong method that replies to ping.
{{#include ../../../../../example/dchat/src/rpc.rs:pong}}
And add it to handle_request():
match req.method.as_str() {
Some("ping") => self.pong(req.id, req.params).await,
Some(_) | None => JsonError::new(ErrorCode::MethodNotFound, None, req.id).into(),
}